24-year trends in incidence and mortality of nephrotic syndrome – a population-based cohort study.

BACKGROUND: Due to increasing prevalence of risk factors for nephrotic syndrome, updated epidemiological data on nephrotic syndrome are needed. We examined the age- and sex-specific incidence, histopathology, and mortality of nephrotic syndrome over 24 years. METHODS: This nationwide cohort study included all adults with first-time recorded nephrotic syndrome in Denmark during 1995-2018 using the Danish National Patient Registry. Data on age, sex, hospital-diagnosed comorbidities, and histopathological findings were obtained. We computed overall, and age- and sex-specific, incidence rates of nephrotic syndrome, 1- and 5-year mortality by calendar period, and 1-year hazard ratios (HRs) of death using Cox models. RESULTS: We identified 3,970 adults with first-time nephrotic syndrome. The incidence was highest in men and increased with age to 11.77 per 100,000 person-years (95%-confidence interval [CI]: 10.21-13.32) in men aged 80+ years, and 6.56 per 100,000 person-years (95%-CI: 5.71-7.41) in women aged 80+ years. The incidence of nephrotic syndrome increased from 3.35 per 100,000 person-years (95%-CI: 3.12-3.58) in 1995-2000 to 4.30 per 100,000 person-years (95%-CI: 4.05-4.54) in 2013-2018. Over time, the 1-year mortality of nephrotic syndrome was stable at 13%-16%, but the HR of death was 0.54 (95%-CI: 0.42-0.69) in 2013-2018 compared with 1995-2000 when adjusted for age, sex, and comorbidities. Sub-distribution of glomerulopathies was stable over time with membranous nephropathy and minimal change disease being the most common. CONCLUSION: During 1995-2018, the incidence of recorded adult nephrotic syndrome increased slightly, and the adjusted mortality of nephrotic syndrome decreased markedly. Whether these findings reflect changes in epidemiology, or in awareness and coding of nephrotic syndrome, remains to be clarified